Stop bfs early when possible
Summary: When doing bfs with given endpoint, we can stop the traversal on first successful pull. Reviewers: teon.banek, msantl, mculinovic, buda Reviewed By: msantl Subscribers: pullbot Differential Revision: https://phabricator.memgraph.io/D1469
This commit is contained in:
Marin Tomic
Teon Banek
parent
1c2f599a93
commit
e2f9eb6fa5
@ -1079,8 +1079,10 @@ class ExpandBfsCursor : public query::plan::Cursor {
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// if current is still empty, it means both are empty, so pull from
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// input
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if (to_visit_current_.empty()) {
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if (skip_rest_ || to_visit_current_.empty()) {
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if (!input_cursor_->Pull(frame, context)) return false;
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to_visit_current_.clear();
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to_visit_next_.clear();
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processed_.clear();
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auto vertex_value = frame[self_.input_symbol_];
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@ -1098,6 +1100,7 @@ class ExpandBfsCursor : public query::plan::Cursor {
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? EvaluateInt(evaluator, self_.upper_bound_,
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"Max depth in breadth-first expansion")
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: std::numeric_limits<int>::max();
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skip_rest_ = false;
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if (upper_bound_ < 1)
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throw QueryRuntimeException(
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"Max depth in breadth-first expansion must be greater then "
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@ -1137,6 +1140,9 @@ class ExpandBfsCursor : public query::plan::Cursor {
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TypedValue &node = frame[self_.node_symbol_];
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// due to optional matching the existing node could be null
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if (node.IsNull() || (node != expansion.second).Value<bool>()) continue;
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// there is no point in traversing the rest of the graph because bfs
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// can find only one path to a certain node
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skip_rest_ = true;
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} else
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frame[self_.node_symbol_] = expansion.second;
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@ -1163,6 +1169,9 @@ class ExpandBfsCursor : public query::plan::Cursor {
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int lower_bound_{-1};
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int upper_bound_{-1};
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// when set to true, expansion is restarted from a new source
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bool skip_rest_{false};
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// maps vertices to the edge they got expanded from. it is an optional
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// edge because the root does not get expanded from anything.
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// contains visited vertices as well as those scheduled to be visited.
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@ -1203,76 +1212,82 @@ class DistributedExpandBfsCursor : public query::plan::Cursor {
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while (true) {
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TypedValue last_vertex;
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if (current_depth_ >= lower_bound_) {
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for (; pull_pos_ != subcursor_ids_.end(); ++pull_pos_) {
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auto vertex = db_.db().bfs_subcursor_clients().Pull(
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pull_pos_->first, pull_pos_->second, &db_);
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if (vertex) {
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last_vertex = *vertex;
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SwitchAccessor(last_vertex.ValueVertex(), self_.graph_view_);
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break;
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if (!skip_rest_) {
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if (current_depth_ >= lower_bound_) {
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for (; pull_pos_ != subcursor_ids_.end(); ++pull_pos_) {
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auto vertex = db_.db().bfs_subcursor_clients().Pull(
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pull_pos_->first, pull_pos_->second, &db_);
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if (vertex) {
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last_vertex = *vertex;
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SwitchAccessor(last_vertex.ValueVertex(), self_.graph_view_);
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break;
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}
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VLOG(10) << "Nothing to pull from " << pull_pos_->first;
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}
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VLOG(10) << "Nothing to pull from " << pull_pos_->first;
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}
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}
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if (last_vertex.IsVertex()) {
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// Handle existence flag
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if (self_.existing_node_) {
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TypedValue &node = frame[self_.node_symbol_];
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// Due to optional matching the existing node could be null
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if (node.IsNull() || (node != last_vertex).ValueBool()) continue;
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} else {
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frame[self_.node_symbol_] = last_vertex;
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}
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VLOG(10) << "Expanded to vertex: " << last_vertex;
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if (last_vertex.IsVertex()) {
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// Handle existence flag
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if (self_.existing_node_) {
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TypedValue &node = frame[self_.node_symbol_];
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// Due to optional matching the existing node could be null
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if (node.IsNull() || (node != last_vertex).ValueBool()) continue;
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// There is no point in traversing the rest of the graph because BFS
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// can find only one path to a certain node.
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skip_rest_ = true;
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} else {
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frame[self_.node_symbol_] = last_vertex;
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}
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// Reconstruct path
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std::vector<TypedValue> edges;
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VLOG(10) << "Expanded to vertex: " << last_vertex;
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// During path reconstruction, edges crossing worker boundary are
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// obtained from edge owner to reduce network traffic. If the last
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// worker queried for its path segment owned the crossing edge,
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// `current_vertex_addr` will be set. Otherwise, `current_edge_addr`
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// will be set.
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std::experimental::optional<storage::VertexAddress>
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current_vertex_addr = last_vertex.ValueVertex().GlobalAddress();
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std::experimental::optional<storage::EdgeAddress> current_edge_addr;
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// Reconstruct path
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std::vector<TypedValue> edges;
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while (true) {
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DCHECK(static_cast<bool>(current_edge_addr) ^
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static_cast<bool>(current_vertex_addr))
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<< "Exactly one of `current_edge_addr` or `current_vertex_addr` "
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"should be set during path reconstruction";
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auto ret = current_edge_addr
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? db_.db().bfs_subcursor_clients().ReconstructPath(
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subcursor_ids_, *current_edge_addr, &db_)
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: db_.db().bfs_subcursor_clients().ReconstructPath(
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subcursor_ids_, *current_vertex_addr, &db_);
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edges.insert(edges.end(), ret.edges.begin(), ret.edges.end());
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current_vertex_addr = ret.next_vertex;
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current_edge_addr = ret.next_edge;
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if (!current_vertex_addr && !current_edge_addr) break;
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// During path reconstruction, edges crossing worker boundary are
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// obtained from edge owner to reduce network traffic. If the last
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// worker queried for its path segment owned the crossing edge,
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// `current_vertex_addr` will be set. Otherwise, `current_edge_addr`
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// will be set.
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std::experimental::optional<storage::VertexAddress>
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current_vertex_addr = last_vertex.ValueVertex().GlobalAddress();
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std::experimental::optional<storage::EdgeAddress> current_edge_addr;
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while (true) {
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DCHECK(static_cast<bool>(current_edge_addr) ^
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static_cast<bool>(current_vertex_addr))
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<< "Exactly one of `current_edge_addr` or "
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"`current_vertex_addr` "
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"should be set during path reconstruction";
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auto ret = current_edge_addr
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? db_.db().bfs_subcursor_clients().ReconstructPath(
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subcursor_ids_, *current_edge_addr, &db_)
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: db_.db().bfs_subcursor_clients().ReconstructPath(
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subcursor_ids_, *current_vertex_addr, &db_);
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edges.insert(edges.end(), ret.edges.begin(), ret.edges.end());
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current_vertex_addr = ret.next_vertex;
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current_edge_addr = ret.next_edge;
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if (!current_vertex_addr && !current_edge_addr) break;
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}
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std::reverse(edges.begin(), edges.end());
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for (auto &edge : edges)
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SwitchAccessor(edge.ValueEdge(), self_.graph_view_);
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frame[self_.edge_symbol_] = std::move(edges);
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return true;
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}
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std::reverse(edges.begin(), edges.end());
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for (auto &edge : edges)
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SwitchAccessor(edge.ValueEdge(), self_.graph_view_);
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frame[self_.edge_symbol_] = std::move(edges);
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return true;
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}
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// We're done pulling for this level
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pull_pos_ = subcursor_ids_.begin();
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// We're done pulling for this level
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pull_pos_ = subcursor_ids_.begin();
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// Try to expand again
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if (current_depth_ < upper_bound_) {
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VLOG(10) << "Trying to expand again...";
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current_depth_++;
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db_.db().bfs_subcursor_clients().PrepareForExpand(subcursor_ids_,
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false);
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if (db_.db().bfs_subcursor_clients().ExpandLevel(subcursor_ids_)) {
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continue;
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// Try to expand again
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if (current_depth_ < upper_bound_) {
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VLOG(10) << "Trying to expand again...";
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current_depth_++;
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db_.db().bfs_subcursor_clients().PrepareForExpand(subcursor_ids_,
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false);
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if (db_.db().bfs_subcursor_clients().ExpandLevel(subcursor_ids_)) {
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continue;
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}
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}
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}
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@ -1294,6 +1309,7 @@ class DistributedExpandBfsCursor : public query::plan::Cursor {
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? EvaluateInt(evaluator, self_.upper_bound_,
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"Max depth in breadth-first expansion")
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: std::numeric_limits<int>::max();
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skip_rest_ = false;
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if (upper_bound_ < 1) {
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throw QueryRuntimeException(
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@ -1323,6 +1339,9 @@ class DistributedExpandBfsCursor : public query::plan::Cursor {
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int lower_bound_{-1};
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int upper_bound_{-1};
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// When set to true, expansion is restarted from a new source.
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bool skip_rest_{false};
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// Current depth. Reset for each new expansion, the initial value is
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// irrelevant.
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int current_depth_{-1};
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